In recent years, electrowetting elements which utilize electrowetting effects have been attracting attention. Generally, an electrowetting element consists of a pair of substrates, and a liquid having relatively high surface energy and a liquid having relatively low surface energy, which are not mixed together, are filled between the pair of substrates. One of the pair of substrates has an electrode layer on a surface thereof, and a hydrophobic middle layer (insulating layer) is formed on a surface of the electrode layer. Electrowetting elements have properties that, when voltages are applied between hydrophilic liquids and electrode layers through hydrophobic middle layers, the hydrophilic liquids are attracted to the hydrophobic middle layers, and thus shapes of interfaces between the hydrophilic liquids and the hydrophobic liquids are altered. By utilizing such properties, electrowetting elements are used for optical lenses, display elements and the like (Non Patent Document 1).
As methods for manufacturing electrowetting elements described above, the methods disclosed in the following Patent Documents 1 and 2 have been known.
In the manufacturing method disclosed in Patent Document 1, a substrate surface is covered with a liquid having high surface energy (water), and an opening is provided on top of the substrate surface. Note that the substrate surface has hydrophobic first regions, and each of the first regions is surrounded by second hydrophilic regions (pixel walls).
When an injector, in which a low surface energy liquid (oil) is filled, ejects oil so as to move the oil along the substrate surface, drops of the low surface energy liquid are drawn into the first region, and a high surface energy liquid contacted with the first region is substituted with a layer of the low surface energy liquid.
Also, in the method for manufacturing an electrowetting device disclosed in Patent Document 2, first and second liquids in which one of them is conductive (high surface energy) and the other is insulative (low surface energy) are used, and the method comprises steps of making a chamber having a liquid inlet and a liquid outlet, and sealing the inside of the chamber by closing the liquid inlet and the liquid outlet after the first liquid and the second liquid are in turn introduced to the inside of the chamber.